Site by Bennett Web & Design Co.
2007 SOUTHEASTERN NATURALIST 6(3):381–392
Population Dynamics of Nine-Banded Armadillos:
Insights from a Removal Experiment
Colleen M. McDonough1,*, J. Mitchell Lockhart1, and W.J. Loughry1
Abstract - From 1992 to 2003, we captured and permanently marked 829 Dasypus
novemcinctus (nine-banded armadillo) at the Tall Timbers Research Station in northern
Florida. From 2004 to 2006, an attempt was made to eliminate all armadillos
from Tall Timbers as part of an experiment to remove nest predators of Colinus
virginianus (Northern Bobwhite). Data from armadillos killed at Tall Timbers during
this period showed a rapid decline in previously marked individuals, with only 4
collected in 2006. Even though the resident population thus seemed to have been
exterminated quickly, total numbers of armadillos collected remained stable over all
3 years. This did not appear to be due to an increase in reproductive success such that
more juveniles were produced to replace the animals being lost. Rather, the data were
more consistent with the hypothesis of immigration by adults into the population to
colonize areas vacated by culled animals. This scenario supports previous reports of
large numbers of transient armadillos that move extensively, and may provide insight
into how armadillos have successfully invaded most of the southern United States in
just the last 200 years. Finally, these findings also suggest that, at least in this area,
culling animals is not likely to be an effective means of eliminating armadillo
predation on quail eggs.
Standard population biology models identify birth and death rates, and
the rates of immigration versus emigration as key determinants of population
size (e.g., Caughley 1977, Hastings 1997, Hedrick 1984, MacArthur and
Connell 1966). Thus, in the face of heightened mortality, the only way for a
population to remain stable is to enhance reproduction and/or to receive
more immigrants. Conventional wisdom suggests increased immigration
would be a less important factor because dispersal is risky, low frequency,
and typically not focused in specific directions (Chepko-Sade and Halpin
1987, Clobert et al. 2001, Stenseth and Lidicker 1992). Consequently, the
probability of large numbers of immigrants moving in to replace individuals
lost through increased mortality would seem low.
Recently, conservation biologists have been interested in identifying
attributes that might make a particular species a successful invader of new
habitats (Sakai et al. 2001). One obvious such trait is vagility, as increased
movement would presumably increase the probability of finding hospitable
areas in which to thrive. Unlike the scenario described above, such populations
might be able to recover quite quickly from population downturns,
even without elevated reproductive rates, due to the extreme fluidity of
individual movement patterns.
1Department of Biology, Valdosta State University, Valdosta, GA 31698-0015. *Corresponding
author - email@example.com.
382 Southeastern Naturalist Vol. 6, No. 3
Dasypus novemcinctus Linneaus (nine-banded armadillo) is a ubiquitous
resident of the southern United States. However, its commonness in the US
is a relatively recent phenomenon; armadillos were first noted in the Rio
Grande River Valley of Texas in the 1820s (Humphrey 1974, Taulman and
Robbins 1996). Coupled with one or more releases of captive armadillos in
south-central Florida in the 1920s, the species has rapidly spread across
much of the southern US, currently found as far north as southern Illinois
and Nebraska (Freeman and Genoways 1998, Van Deelen et al. 2002) and
possibly as far west as Arizona (M. Mares, Sam Noble Oklahoma Museum
of Natural History, University of Oklahoma, Normal, OK, pers. comm.).
Taulman and Robbins (1996) estimated that armadillos were expanding
their range in the US at the rate of 4 km/yr. This would suggest substantial
movement by individuals out of established populations to colonize new areas.
In a long-term study of patterns of recruitment and retention in an armadillo
population, Loughry and McDonough (2001) found that a certain portion of the
animals were long-term residents that moved very little (see also Gammons
2006). However, in addition, many animals were captured only once, seemingly
as they passed through the area. These animals have been referred to as
transients (Bond et al. 2000, Jacobs 1979). What determines whether an
armadillo becomes a long-term resident versus a transient remains unknown at
present, but it seems likely that transients are major factors in promoting the
rapid range expansion of nine-banded armadillos in the United States.
Recent intensive studies of Colinus virginianus Linneaus (Northern
Bobwhite) nests have identified nine-banded armadillos as an important
mammalian predator of quail eggs (Staller 2001, Staller et al. 2005). Consequently,
there has been interest among game managers in finding ways to
limit this predation and improve quail production. One proposed option is
to remove all potential mammalian predators from quail-nesting habitat.
However, such an approach is only likely to be effective if culled animals
are not replaced (via immigration or increased reproduction), so that
predator populations are permanently reduced. In the case of nine-banded
armadillos, the presence of transients and the rapid range expansion of this
successful invader suggest there may be a considerable reservoir of individuals
available to replace those lost.
From 1992 to 2003 we studied a population of nine-banded armadillos at
the Tall Timbers Research Station. A major component of this study involved
extensive mark-recapture sampling. Beginning in 2004, Tall Timbers
contracted with the United States Department of Agriculture (USDA) to
conduct a 3-year experiment in which all potential mammalian predators of
Northern Bobwhite eggs were removed from the property. Thus, armadillos,
along with other species such as Lynx rufus Schreber (bobcat), Procyon
lotor Linneaus (raccoon), Canis latrans Say (coyote) and Didelphis
virginiana Kerr (opossum), were trapped and killed from 2004 to 2006. This
massive undertaking provided a unique opportunity to examine certain
features of armadillo population dynamics. Specifically, data from these
2007 C.M. McDonough, J.M. Lockhart, and W.J. Loughry 383
harvested animals allowed us to address the following questions: (1) How
long did it take to remove the resident population of armadillos from Tall
Timbers? (2) Once residents were gone, were they replaced—either from
within the population by increased production of juveniles, or from without
by increased immigration of adults into vacated spaces—or did the population
show a steady decline toward local extinction? and (3) Is culling
animals an effective means of reducing armadillo predation on quail eggs?
Study Site Description
Tall Timbers is located north of Tallahassee, Fl (Leon County) at the
border with Georgia. The 1600-ha property is situated along the north shore of
Lake Iamonia and is bisected by a public road (County Road 12, Fig. 1). Major
habitat types found there are: (1) hammocks, or bottomland hardwood forests,
consisting primarily of: Quercus spp. (oak), Fagus grandifolia Ehrh. (American
beech), and Magnolia grandiflora L. (southern magnolia); (2) fields,
which were plowed annually and planted with Zea mays L. (corn), Trifolium
spp. (clover), and Urochloa ramosa (L.) Nguyen (brown-top millet); and (3)
upland pine, primarily consisting of Pinus taeda L. (loblolly), P. echinata P.
Mill. (shortleaf), and some P. palustris P. Mill. (longleaf), along with some
shrubby undergrowth (Brennan et al. 1998, McDonough et al. 2000).
Details of sampling conducted between 1992–2003 can be found in
Loughry and McDonough (2001) and McDonough and Loughry (2005).
Briefly, with the exceptions of 1996 and 2000, we censused the armadillo
population at Tall Timbers for approximately 3 months each summer (see
Robertson et al. 2000). Censuses were conducted at all hours, but primarily
in the evenings, from about 16:00–24:00. We attempted to capture all
animals observed while walking or driving along roads and trails on the
property. For each captured animal, various body-size measurements,
weight, and sex were recorded (Loughry and McDonough 1996), and the
reproductive condition of females was assessed by examination of the
nipples (see Loughry and McDonough 1996). In addition, one or more small
pieces of ear tissue were obtained for genetic analyses using an ear notcher
(e.g., Prodöhl et al. 1996), and the spatial location of the animal was
obtained with a handheld GPS unit (Loughry and McDonough 1998). Animals
were permanently marked with passive induced transponder (PIT) tags
injected under the front carapace immediately behind the neck. These PIT
tags, coupled with natural markings such as scars, missing tail segments, etc.
(Loughry et al. 2002), and the fact that ear notches were taken from different
locations on each ear for each animal, allowed us to reliably identify individual
armadillos when recaptured during subsequent years.
Elimination of armadillos at Tall Timbers was conducted from 1 March–
30 September of 2004–2006. Extermination was accomplished in two ways:
384 Southeastern Naturalist Vol. 6, No. 3
Figure 1. Map of Tall Timbers Research Station showing locations of sampled
armadillos. A. Locations (n = 2047) of animals sampled via mark-recapture from
1992 to 2003 (modified from McDonough and Loughry 2005). Data include multiple
locations from the same individuals to provide the broadest depiction of the sampled
area. B. Locations (n = 451) of animals harvested by the USDA, 2004–2006. Not all
locations are depicted in either figure because of extreme overlap among some
points. Stippled areas represent open water; the lower edge of the property is
bounded by Lake Iamonia.
2007 C.M. McDonough, J.M. Lockhart, and W.J. Loughry 385
with baited leg-hold and live traps and by shooting animals encountered
while on the property. Traps were used for catching not only armadillos, but
all mammalian predators of interest. A total of 125 traps were placed at a
variety of locations on the property for an average of 25,625 trap-nights per
year. Culled animals were sexed and weighed. Weights were used to assign
individuals to age classes as juveniles or adults (Loughry and McDonough
1996; note that for the purposes of this study, yearling individuals were
categorized as adults). All culled animals were part of a larger wildlife
disease study (J.M. Lockhart et al., unpubl. data) in which the carcasses were
dissected, but unfortunately no data on female reproductive condition (pregnant,
lactating, etc.) were taken.
In addition to Tall Timbers, the USDA replicated their experiment at
three other sites. Armadillos were harvested from Pebble Hill Plantation,
located just south of Thomasville, GA, from 2001 to 2003. They were also
removed from two separate tracts at Pinebloom Plantation, located just west
of Albany, GA. Pinebloom A was harvested from 2001 to 2003, and
Pinebloom B from 2004 to 2006. Although we did not have baseline data
from these sites, we include some data from them to assess how generalized
the results were from Tall Timbers.
Prior to 2004, simple mark-recapture estimates of population size indicated
an armadillo population at Tall Timbers numbering approximately 400
individuals (Lincoln-Peterson index calculated between successive years
from 1992 to 2003; C.M. McDonough, unpubl. data). In general, slightly
less than 40% of the animals caught in any given year were residents that had
been caught previously (Table 1). New animals were either juveniles or
adults that had never been caught before. Of these adults, some were only
caught in one year and never again, while others settled in the population and
were recaptured in later years.
Due to a combination of factors, including drought and an extensive
removal of hardwoods, the armadillo population at Tall Timbers declined
between 2001–2003 (McDonough and Loughry 2005). Analyzing the effects
of harvesting could potentially be biased by the atypical conditions occurring
during this period. To minimize this problem we performed two sets of
analyses. First, we used data from just 2003 as the most recent exemplar
of the unharvested condition (Table 1). We then used long-term data, obtained
by averaging yearly values from 1992 to 2002 (Table 1), to obtain a
Table 1. Demography of D. novemcinctus (nine-banded armadillo) during 12 years of markrecapture
sampling at Tall Timbers Research Station. Data for 1992–2002 are yearly averages ±
SD. Total caught includes some animals that could not be assigned to a particular age/sex category.
Total caught 132.44 ± 59.99 58
Adult males 57.78 ± 28.46 24
Adult females 51.00 ± 29.24 24
Juvenile males 11.44 ± 5.39 5
Juvenile females 10.56 ± 7.40 4
Number of recaptures 50.75 ± 33.80 15
386 Southeastern Naturalist Vol. 6, No. 3
more general picture of how harvesting impacted the population. With these
data, we used chi-square tests to compare proportions of juveniles and
proportions of previously marked animals in the population before and
during harvesting. We also used chi-square tests to determine if any sex
differences occurred among the new and recaptured animals collected during
harvesting (versus the null hypothesis of a 50:50 sex ratio in each case),
and to examine year-to-year changes in the numbers of animals collected at
each of the four harvested sites (performed by comparing the proportion of
total animals collected at each site in pair-wise tests between years).
We marked a total of 829 armadillos from 1992 to 2003; 451 animals
were removed by the USDA from 2004 to 2006. Armadillos are not normally
considered easily trappable animals, but these results indicate trapping was
surprisingly effective. Coupled with opportunistic shooting of animals, it
thus appears culling of armadillos each year was thorough and extensive.
Visual inspection of locations where we live-caught animals (Fig. 1A) and
locations where armadillos were trapped or shot (Fig. 1B) indicate our
marked population was subject to intense harvesting by the USDA (note that
both figures only depict successful captures; sampling in both instances was
more extensive because some areas were sampled where no armadillos were
ever caught). Thus, we are confident the results we report are not due to
some form of sampling bias.
The marked population of armadillos at Tall Timbers was rapidly eliminated:
of the 41 marked animals collected, 78% were taken in 2004
(Table 2). The proportion of marked animals collected in 2004 was significantly
greater than in 2005 (2= 20.86, P < 0.0001) and 2006 (2 = 23.81,
P < 0.0001); the proportion of marked animals collected in 2005 versus 2006
did not differ (2 = 0.001, P = 0.96). Likewise, the proportion of marked
animals collected in 2004 was similar to that in 2003 (2= 0.24, P = 0.62),
but the proportions in 2005 and 2006 were significantly lower (both P <
0.0001). Use of longer-term data from 1992–2002 showed the proportion of
marked animals in the culled samples was significantly lower in all 3 years
Table 2. Demography of D. novemcinctus (nine-banded armadillo) killed at Tall Timbers
Research Station during 3 years of intensive culling. All previously marked animals were adults
when killed (M = male, F = female). Total killed is larger than the sums of values for age/sex
classes because some animals were missing data and so could not be assigned to a particular age
and sex group.
2004 2005 2006
Total killed 149 149 153
Adult males 56 65 59
Adult females 54 49 66
Juvenile males 16 17 11
Juvenile females 17 8 5
Number marked (M/F) 32 (16/16) 5 (2/3) 4 (2/2)
2007 C.M. McDonough, J.M. Lockhart, and W.J. Loughry 387
(all P < 0.003). There were no sex differences in animals collected at Tall
Timbers, either among previously marked animals (all P > 0.48) or among
new adults (all P > 0.32) or juveniles (all P > 0.25).
The proportion of armadillos collected each year did not change significantly
(pair-wise comparisons between years, all P > 0.83, Fig. 2).
Interestingly, a similar pattern was found at one of the three other sites that
also harvested armadillos for three years (Pinebloom A: pair-wise comparisons
between years, all P > 0.38, see Fig. 2). At the other two (Pinebloom
B and Pebble Hill), proportions of collected animals were significantly
greater in year 1 than in year 2 (both P < 0.003) and year 3 (both P <
0.0005), but not between year 2 and year 3 (both P > 0.08, see Fig. 2).
Numbers of juveniles collected were low (Table 2) and the proportion of
juveniles in the population each year did not differ significantly from numbers
live-caught in 2003 (all P > 0.38) or 1992–2002 (all P > 0.17), indicating
production of juveniles did not increase with the onset of harvesting. Further,
comparisons of proportions of juveniles in the culled population each year
showed a significant decrease between 2004 and 2006 (2 = 6.57, P = 0.009;
other pair-wise comparisons between years were not significant, all P > 0.15),
the opposite of what might be expected if increased reproduction was responsible
for the replacement of culled individuals.
Our data document remarkable constancy of the armadillo population
at Tall Timbers in the face of intensive harvesting. As discussed below, it
seems unlikely this was due to increased production and retention of
Figure 2. Numbers of D. novemcinctus (nine-banded armadillo) culled by the USDA
at four sites over three years. Sampling at Pebble Hill and Pinebloom A occurred
from 2001 to 2003, and at Tall Timbers and Pinebloom B from 2004 to 2006.
388 Southeastern Naturalist Vol. 6, No. 3
juveniles in their natal population. Rather, it appears there was a substantial
pool of animals in the surrounding habitat available to immigrate in
and rapidly replace individuals that were removed.
Although a crude estimate, Lincoln-Peterson calculations of armadillo
population size at Tall Timbers suggested nearly 400 individuals inhabited
the site per year. However, the population appeared to be in decline during
2001–2003 due to the effects of a prolonged drought and habitat alterations
resulting from an extensive hardwood removal (McDonough and Loughry
2005). Thus, at the start of harvesting by the USDA, the total population at
Tall Timbers was probably much lower. If so, then assuming minimal
replacement, the numbers of animals culled in 2004 and 2005 (Table 2)
should have virtually eliminated the entire population. Yet, remarkably, the
number of armadillos taken in 2006 actually slightly exceeded the numbers
taken in each of the previous two years.
One might expect the rapid elimination of the marked animals at Tall
Timbers to result in an overall decline in the population. However, the
proportion of armadillos collected each year did not change significantly
(Fig. 2), as also was the case with the population at the Pinebloom A Tract.
So from where did all these animals come? Based on the data in Table 2,
it seems unlikely they were resident animals that managed to escape capture
in previous years. Indeed, animals marked by us from 1992 to 2003 were
nearly gone after just one year of harvesting, suggesting much of the resident
population was quickly eliminated. Given that fact, maintenance of a stable
population size at Tall Timbers in the face of such an intense harvesting
effort only seems possible if either there was (a) a considerable increase in
reproduction, producing enough juveniles to replace animals being lost, and/
or (b) increased immigration into the population by animals colonizing areas
vacated by culled individuals. Our data are most consistent with the latter
hypothesis, since increased reproduction seems unlikely. Female ninebanded
armadillos give birth to a single litter of genetically identical quadruplets
each year (Prodöhl et al. 1996), although not all females reproduce
every year. Thus, replacement of culled animals by reproduction would
require either an increase in the number of reproductive females and/or
increased survivorship of juveniles. Neither seems likely because (a) the
numbers of juveniles collected each year was not significantly increased
over that seen in earlier years, and (b) many pregnant and lactating females
were probably killed in the spring and summer, presumably resulting in the
loss of many litters. Studies of territorial species have documented many
instances of non-territorial floaters that exist within a population waiting to
fill any vacancies that might occur (reviews in Greenwood and Harvey 1982,
Kokko and Sutherland 1998, Pen and Weissing 2000, Reed et al. 1999,
Smith 1978). It is not clear if such individuals exist in nine-banded armadillo
populations. However, even if they do, the harvesting protocol should have
eliminated them as well, so it seems unlikely replacements for culled animals
came from any within-population source.
2007 C.M. McDonough, J.M. Lockhart, and W.J. Loughry 389
Given our results, the most likely explanation for the continued high
abundance of armadillos at Tall Timbers is that culled animals were rapidly
replaced by immigrants. Even though relatively close to an urban environment,
Tall Timbers is not an isolated island of suitable armadillo habitat and
may not represent a distinct population. Large tracts of relatively undisturbed
land border the property and presumably harbor many armadillos.
These areas represent a potentially large reservoir of individuals that could
replace those lost at Tall Timbers. Of course, this assumes these individuals
move sufficiently to discover the newly available openings. Our previous
work has shown that some armadillos are long-term residents that remain in
the same areas year after year (up to 10 years; Loughry and McDonough
2001). However, an additional component of the population is made up of
individuals that are caught once and never again. Bond et al. (2000) referred
to these individuals as transients, suggesting they were temporary members
of the population, captured as they moved through the area. The existence of
transients would seem necessary to explain the rapid and continued range
expansion of nine-banded armadillos in the United States, which can only be
generated by the movement of individuals out of established populations to
colonize new areas. Thus, even if floaters do not exist within armadillo
populations, the extensive movements of transient individuals would suggest
sufficient vagility and fluidity to not only colonize new habitats, but
also to fill vacancies created in established populations (Gammons 2006).
Further understanding of armadillo population dynamics will require identifying
the factors that distinguish transients from residents, coupled with
genetic analyses of gene flow between populations to identify the extent and
sources of immigrants into established populations.
Given the nature of this study, only immigration could be the major source
of new individuals in the population because juveniles and reproductive adults
were continually eliminated. Obviously, under more natural conditions reproduction
and immigration would undoubtedly both contribute to maintaining
population levels. However, our data indicate that immigration can maintain
population size even in the absence of much reproductive input. High juvenile
mortality (McDonough and Loughry 1997), coupled with the fact that we
found no evidence that reproduction increased in the face of population
decline (and in fact decreased in 2006), would suggest that, even under more
natural conditions, immigration may be more important than reproduction in
restoring population size. Of course, this is more likely to be true in areas
saturated with armadillos, where individuals from surrounding habitats can
easily move into vacated areas. Immigration is probably less important (and
reproduction more important) in more isolated populations, e.g., along the
expanding northern edge of the species’ range.
The data from the first year of harvesting in 2004 show a population
substantially larger than that observed in 2003. As stated above, markrecapture
data indicated a population in decline from 2001 to 2003, probably
due to the combined effects of drought and habitat changes associated with
extensive logging of hardwoods on the property. More animals might be
expected from sampling in 2004 because the sampling period was over twice
390 Southeastern Naturalist Vol. 6, No. 3
as long (7 months in 2004 versus 3 months in 2003) and the area sampled
was larger. With regard to the latter, we did catch and mark armadillos in
almost all areas of the property (Fig. 1A), but our sampling was primarily
concentrated in the bottomland hardwoods along the lakefront; sampling in
the northern part of the property (in particular north of County Road 12) was
much less extensive. In contrast, USDA sampling was more equally distributed
across the entire property and so might have contributed to the
increased sample size obtained. Nonetheless, much of the habitat in the other
areas sampled by the USDA was upland pine, and previous work has shown
that few armadillos are normally found there (McDonough et al. 2000).
Thus, it appears that, while increased sampling effort may have contributed
somewhat to the increased numbers of animals collected in 2004, the population
may also have been recovering from the decline associated with drought
and hardwood removal, suggesting the effects of these impacts were not as
long-lasting as previously supposed (McDonough and Loughry 2005). This
is, perhaps, not surprising in such a successful invasive species as ninebanded
armadillo. The rapid range expansion of this species in the US would
seem to require properties such as resiliency and an ability to quickly adjust
to new conditions, a view reinforced by the data presented here.
There are at least two questions regarding our data that we cannot answer
at present. First, why were so many more armadillos collected at Tall Timbers
than any other site (see Fig. 2)? All four sites were intentionally designed to
be replicates, so the difference cannot be explained by differences in sampling
effort or size of the sampled areas. In addition, Tall Timbers possesses
similar habitat features as the other sites, so there are no obvious characteristics
of this one site that would suggest it is somehow superior for armadillos.
Perhaps a broader, metapopulation perspective of surrounding areas might be
relevant, but at present no obvious explanation exists for this difference
between sites. Second, we have argued above that immigration of transients
allowed maintenance of the Tall Timbers population in the face of extensive
harvesting. However, because animals continued to be killed each year of the
study, we cannot know the long-term fate of these individuals. Clearly,
transients moved into the areas vacated by culled animals. But, did they settle
in these areas or continue as transients? Now that culling of animals has
ceased at Tall Timbers, this question could be answered by tracking the
population over the next few years.
This study was possible because of the interest in assessing the impact of
nest-predator removal on Northern Bobwhite reproductive success. Given
that a large suite of mammalian predators was eliminated at Tall Timbers
(n = 1446 individuals collected from all species combined; J.M. Lockhart,
unpubl. data), it is possible the experiment generated positive results. However,
looking specifically at the armadillo data, it is hard to envision harvesting
as an effective management strategy. At 2 of the 4 sites where harvesting
occurred, the numbers of armadillos taken remained stable over the 3 years
of the experiment (Pinebloom A and Tall Timbers, see Fig. 2); harvesting
did impact populations at the other 2 sites, where the number of animals
collected in the third year of the study was 50% or less of that taken in the
2007 C.M. McDonough, J.M. Lockhart, and W.J. Loughry 391
first year (Fig. 2). There are no data available to assess to what extent these
populations may have rebounded after harvesting ended, but the data from
Tall Timbers suggest replacement can be very rapid. Harvesting is difficult,
labor-intensive work. Given its minimal impact in 2 populations and, in
particular, the rapid replacement of individuals at Tall Timbers, it would
seem that, even if partially effective in the short-term, unless there is a longterm
commitment to persistent culling, such a strategy is ultimately doomed
to failure in controlling armadillo populations.
We thank the staff of Tall Timbers Research Station for allowing us to work there
for so many years. We also thank the USDA personnel, Hardy S. Drew, John C.
Griffin, Lucas B. Harvard III, Daymond W. Hughes, Patrick H. Stalvey, and Orin B.
White, Jr., who collected all the animals. We are grateful to the Guest Editor, Lenny
Brennan, and two anonymous reviewers for their helpful comments. Our work at Tall
Timbers was funded over the years by Faculty Research Awards from Valdosta State
University, Earthwatch, and the American Philosophical Society.
Bond, B.T., M.I. Nelson, and R.J. Warren. 2000. Home-range dynamics and den use
of nine-banded armadillos on Cumberland Island, Georgia. Proceedings of the
Annual Conference of Southeastern Fish and Wildlife Agencies 54:414–424.
Brennan, L.A., R.T. Engstrom, S.M. Hermann, S.T. Lindeman, W.K. Moser, K.
McGorty, J. Noble, and W.E. Palmer. 1998. A five-year land-management plan
for Tall Timbers Research Station property: 1998–2002. Tall Timbers Research
Station, Tallahassee, FL. 106 pp.
Caughley, G. 1977. Analysis of Vertebrate Populations. John Wiley and Sons, New
York, NY. 234 pp.
Chepko-Sade, B.D., and Z.T. Halpin (Eds.). 1987. Mammalian Dispersal Patterns.
University of Chicago Press, Chicago, IL. 342 pp.
Clobert, J., E. Danchin, A.A. Dhondt, and J.D. Nichols (Eds.). 2001. Dispersal.
Oxford University Press, Oxford, UK. 452 pp.
Freeman, P.W., and H.H. Genoways. 1998. Recent northern records of the nine-banded
armadillo (Dasypodidae) in Nebraska. Southwestern Naturalist 43:491–504.
Gammons, D. 2006. Radiotelemetry studies of armadillos in southwestern Georgia.
M.Sc. Thesis. University of Georgia, Athens, GA. 75 pp.
Greenwood, P.J., and P.H. Harvey. 1982. The natal and breeding dispersal of birds.
Annual Review of Ecology and Systematics 13:1–21.
Hastings, A. 1997. Population Biology: Concepts and Models. Springer, New
Hedrick, P.W. 1984. Population Biology: The Evolution and Ecology of Populations.
Jones and Bartlett, Boston, MA. 445 pp.
Humphrey, S.R. 1974. Zoogeography of the nine-banded armadillo (Dasypus
novemcinctus) in the United States. BioScience 24:457–462.
Jacobs, J.F. 1979. Behavior and space-usage patterns of the nine-banded armadillo
(Dasypus novemcinctus) in southwestern Mississippi. M.Sc. Thesis. Cornell
University, Ithaca, NY. 132 pp.
Kokko, H., and W.J. Sutherland. 1998. Optimal floating and queuing strategies:
Consequences for density dependence and habitat loss. American Naturalist
392 Southeastern Naturalist Vol. 6, No. 3
Loughry, W.J., and C.M. McDonough. 1996. Are road kills valid indicators of
armadillo population structure? American Midland Naturalist 135:53–59.
Loughry, W.J., and C.M. McDonough. 1998. Spatial patterns in a population of ninebanded
armadillos (Dasypus novemcinctus). American Midland Naturalist
Loughry, W.J., and C.M. McDonough. 2001. Natal recruitment and adult retention in
a population of nine-banded armadillos. Acta Theriologica 46:393–406.
Loughry, W.J., C.M. McDonough, and E.G. Robertson. 2002. Patterns of anatomical
damage in a population of nine-banded armadillos Dasypus novemcinctus
(Xenarthra, Dasypodidae). Mammalia 66:111–122.
MacArthur, R.H., and J.H. Connell. 1966. The Biology of Populations. John Wiley
and Sons, New York, NY. 200 pp.
McDonough, C.M., and W.J. Loughry. 1997. Patterns of mortality in a population of
nine-banded armadillos, Dasypus novemcinctus. American Midland Naturalist
McDonough, C.M., and W.J. Loughry. 2005. Impacts of land management practices
on a population of nine-banded armadillos in northern Florida. Wildlife Society
McDonough, C.M., M.A. Delaney, P.Q. Le, M.S. Blackmore, and W.J. Loughry.
2000. Burrow characteristics and habitat associations of armadillos in Brazil and
the United States of America. Revista de Biología Tropical 48:109–120.
Pen, I., and F.J. Weissing. 2000. Optimal floating and queuing strategies: The logic
of territory choice. American Naturalist 155:512–526.
Prodöhl, P.A., W.J. Loughry, C.M. McDonough, W.S. Nelson, and J.C. Avise. 1996.
Molecular documentation of polyembryony and the micro-spatial dispersion of
clonal sibships in the nine-banded armadillo, Dasypus novemcinctus. Proceedings
of the Royal Society, London, Series B 263:1643–1649.
Reed, J.M., T. Boulinier, E. Danchin, and L.W. Oring. 1999. Informed dispersal:
Prospecting of birds for breeding sites. Current Ornithology 15:189–259.
Robertson, E.G., C.M. McDonough, and W.J. Loughry. 2000. Changes in
observability of adult nine-banded armadillos over the summer: Observer effect
or seasonal decline? Florida Field Naturalist 28:161–172.
Sakai, A.K., F.W. Allendorf, J.S. Holt, D.M. Lodge, J. Molofsky, K.A.With, S.
Baughman, R.J. Cabin, J.E. Cohen, N.C. Ellstrand, D.E. McCauley, P. O’Neil,
I.M. Parker, J.N. Thompson, and S.G. Weller. 2001. The population biology of
invasive species. Annual Review of Ecology and Systematics 32:305–332.
Smith, S.M. 1978. The “underworld” in a territorial species: Adaptive strategy for
floaters. American Naturalist 112:571–582.
Staller, E.L. 2001. Identifying predators and fates of Northern Bobwhite nests using
miniature video cameras. M.Sc. Thesis. University of Georgia, Athens, GA. 53 pp.
Staller, E.L., W.E. Palmer, J.P. Carroll, R.P. Thornton, and D.C. Sisson. 2005.
Identifying predators at Northern Bobwhite nests. Journal of Wildlife Management
Stenseth, N.C., and W.Z. Lidicker. (Eds.). 1992. Animal Dispersal: Small Mammals
as a Model. Chapman and Hall, London, UK. 365 pp.
Taulman, J.F., and L.W. Robbins. 1996. Recent range expansion and distributional
limits of the nine-banded armadillo (Dasypus novemcinctus) in the United States.
Journal of Biogeography 23:635–648.
Van Deelen, T.R., J.D. Parrish, and E.J. Heske. 2002. A nine-banded armadillo
(Dasypus novemcinctus) from central Illinois. Southwestern Naturalist